A typical supermarket includes a rack type refrigeration system wherein a plurality of individual refrigeration cases are placed throughout the supermarket. These cases display and store the supermarket goods requiring cold temperatures to prevent spoilage and/or melting. Each case may include a housing that also contains an expansion valve and evaporator. As the liquid refrigerant passes through the expansion valve, it cools and passes through the evaporator to extract heat therefrom. Fans blow air through the evaporator to extract heat from the air so that a flow of cool air is generated and directed toward the goods to be kept cool.
Each evaporator receives a flow of liquid refrigerant from a central equipment room that houses common refrigeration equipment. The refrigerant gas output from each evaporator is supplied to the input of a common compressor. A common condenser is connected downstream from the compressor to cool the heated compressed refrigerant from the compressor. A common high pressure receiver is connected downstream from the condenser to collect liquid refrigerant. The liquid refrigerant from the receiver is then supplied back to the evaporators.
This conventional type of supermarket refrigeration system requires considerable copper piping to supply the liquid refrigerant to the evaporators, and to return the refrigerant gas back to the compressor. Indeed, a typical supermarket may contain about eight miles of copper piping. Unfortunately, the piping for the return refrigerant gas may still be relatively cool and therefore cause moisture condensation along its outer surface. This moisture is typically collected, such as using drip pans, to avoid wet areas in the supermarket. These pipes are also of a relatively large diameter, for example, about 1⅝ inches. In other words, a considerable investment in piping, maintenance, and moisture control is needed for the conventional supermarket refrigeration system.
Another type of supermarket refrigeration uses self-contained refrigeration cases that include the expansion valve, evaporator, compressor and condenser. These do not require the extensive piping as described above for the rack type system. However, the heat released from the condenser into the interior of the supermarket needs to be removed by the supermarket air conditioning system.
Yet another supermarket refrigeration system is described in U.S. Pat. No. 5,440,894 to Schaeffer et al. The patent discloses a plurality of refrigeration cases connected to a distribution manifold and return manifold. The distribution manifold is connected to evaporators in the refrigeration cases. The evaporators are connected to a common suction header that connects to a number of multiplexed compressors that are connected to a condenser rack.
U.S. Pat. No. 4,748,820 to Shaw discloses a refrigeration system for multiple refrigeration cases in which each refrigeration case has a low-stage booster compressor and an evaporator. The low-stage booster compressor is connected to a manifold that is connected to high-stage compressors. The high-stage compressors are connected to an oil separator and the oil separator is connected to a condenser. The condenser is connected to a receiver that is connected to a liquid distribution manifold that is connected to the evaporator.
U.S. Pat. No. 5,042,268 to LaBrecque discloses a refrigeration system that operates evaporators in both moderate and low refrigerated cases in which respective compressors are associated with each type of evaporator. The compressors are connected downstream of the evaporators and upstream of the receiver. In addition, all the compressors are lubricated by an oil separator using dedicated oil lines.
Unfortunately, current supermarket refrigeration systems may be relatively complicated and expensive, especially where moisture control and/or separate oil lines are used.